Keeping dependencies current is mostly a solved problem, and mostly free. The three tools do overlapping-but-different jobs.
| Cost | Scope | Nature | |
|---|---|---|---|
| Dependabot | free, built into GitHub | 30+ ecosystems, GitHub only | version + security update PRs |
| Renovate | free (Mend-hosted app or self-host, AGPL) | 90+ package managers, GitHub/GitLab/Bitbucket/Azure/Gitea | highly configurable update PRs |
| Snyk | free tier (limited private repos), then per-developer | multi-language | vulnerability scanner first, updates second |
Dependabot is the zero-setup default if you're on GitHub. It's part of the platform, costs nothing, needs no configuration, and covers the basics — version bumps and security advisories as pull requests. For most GitHub repos it's all you need.
Renovate is what you graduate to when you want control: grouped updates, custom schedules, automerge rules for trusted updates, monorepo awareness, and support for far more package managers and Git platforms than Dependabot. The Mend-hosted app is free; you can also self-host under AGPL. Mend sells enterprise add-ons (merge-confidence dashboards, org-wide management) but the core is free. This is the pick for anything non-trivial, or if you're not on GitHub.
Snyk comes at it from security, not housekeeping — it's a vulnerability scanner that also opens fix PRs. If your actual need is "tell me which of my dependencies are exploitable and how reachable the vulnerable code is," Snyk does that and Renovate/Dependabot don't. But it's not a substitute for a general update bot, and the free tier limits private-repo scanning.
GitHub-only and want zero config: Dependabot. Need real control or multi-platform: Renovate. Want security triage with reachability analysis: Snyk, alongside one of the others.